fly » flaw

After all is done if there are no stress cracks
the wheel will probably be as strong as before, but I suspect a flaw in the
ointment, there probably was a defect in the wheel all along. (Antique Tractor forum, Feb. 16, 1999)

They say their motivation is to save the world, when actually it is to be justified according to their “good works”. But the flaw in the ointment, is the fact that those “good works” are judgement and spiritual violence. (XnForums, Nov. 20, 2003)

If my boss gave me a job as head of the financial department because I am an expert neo-classical economist, am I going to resign when I hear of the fatal flaw in the ointment? (Goodshare, Jan. 12, 1997)

There is one fatal flaw in the ointment so to speak. (alt.sailing.asa, Jan. 9, 2002)